[Q] Error installing Framework. topic

Hi, i got a Lenovo A850+, and i've rooted the phone correctly, so any app that requires root can work ;) Now i've installed xposed, but when i try to install the framework, it says that "can't backup /system/bin", and i assume is caused by the fact that the file system is "read only", as i've seen from a command in the terminal. I tried any alternatives to install the framework, but nothing works, even from recovery. I tried so many commands from terminal, but no one works, and the file system is still read only. There's anything i can do to solve this issue i'm having? Thanks for the support :)